1. Technical Field
Embodiments generally relate to the electronics industry and, more specifically, to radio transceiver systems. Embodiments more specifically relate to a directional coupler.
2. Discussion of the Related Art
A coupler is generally used to recover part of the power present on a so-called main or primary transmission line to provide it to another so-called coupled or secondary line, located nearby. Couplers are divided in two categories according to whether they are formed of discrete passive components (it is then spoken of lumped element couplers) or of conductive lines close to one another to be coupled (it is then spoken of distributed couplers). The described embodiments relate to the second category of couplers. The ports of the main line are generally called IN (input) and OUT (output). The ports of the coupled line are generally designated as CPLD (coupled) and ISO (isolated).
In many applications, it is needed to sample part of the power transmitted over a line, for example, to control the power of an amplifier in a transmit system, to control the linearity of a transmit amplifier according to the loss associated with the reception of an antenna, to dynamically match an antenna, to set an impedance matching network, etc. A measurement of the amplitude (and sometimes of the phase) of the signals present on the terminals of the secondary line is used to sample this information.
The use of the information sampled from the secondary line of the coupler generally uses electronic circuits with differential signals. The use of differential signals improves the dynamics, especially for high frequencies (from several hundreds of megahertz to a few gigahertz) more specifically targeted by the present invention.
Converting common-mode signals into a differential signals generally requires specific circuits. In particular, to perform this conversion in the measurement circuit, active circuits connected to the CPLD and ISO terminals are often used.
However, active circuits increase the power consumption. This further increases the measurement circuit bulk.